Altering the therapeutic paradigm towards a distal bowel margin of < 1 cm in patients with low-lying rectal cancer: a systematic review and commentary

Aim The 1-cm rule of distal bowel clearance in patients with low-lying rectal cancer undergoing anterior resection is based mainly on pathological data showing distal intramural spread. Because clinical data are contradictory, a review that includes only cancers located 5 or 6cm from the anal verge was carried out. Method A systematic review of the literature identified seven studies that presented results in relation to a margin of 1cm (n=293) vs >1cm (n=315). In six studies, pre- or postoperative radiotherapy was implemented, and in one study patients were treated with surgery alone. Three studies, all implementing radiotherapy, reported results related to a margin of 5mm (n=51) vs >5mm (n=125). Results In none of the studies were the differences in local recurrence rate between the small and large margin groups statistically significant. The pooled analysis of six studies, in which patients received perioperative radiotherapy, showed a 1.2% [95% confidence interval (Cl) 4.57.0%] higher local recurrence rate in the 1cm margin group compared with the >1cm margin group (P=0.6). The corresponding figures for the 5mm cut-off point were 0.5% (95% CI 7.68.7%, P=0.9). The 5-year local recurrence rate in the only study in which radiotherapy had not been used was 8.6% higher in the 1cm margin group compared with the >1cm margin group (P=0.09). Conclusion Clinical evidence does not support the 1-cm rule in patients with low-lying rectal cancer undergoing pre- or postoperative radiotherapy.